Permineralised Torreya (Taxaceae) leaves from the Upper Cretaceous of Southern Alberta, Canada

The Upper Cretaceous Horseshoe Canyon Formation (HCF) in southern Alberta, Canada, is primarily known for its rich dinosaur fossil fauna but also yields an abundance of plant fossils, including anatomically preserved permineralised plants. We describe a new fossil-species of Taxaceae, Torreya albertensis sp. nov., based on isolated leaves from the silicified flora of the HCF. Torreya albertensis is characterised by linear-lanceolate, slightly falcate leaves with cuneate, twisted bases and cuspidate apices. The epidermal cells on both leaf surfaces are strongly elongated with tapering or oblique ends. The stomatal complexes are irregularly arranged in two deep, longitudinal grooves on the abaxial leaf surface. The subsidiary cells of the stomatal complexes and the ordinary epidermal cells of the stomatal bands bear papillae that are basally fused and form epistomatal chambers. The short and broad leaf shape and comparatively short epidermal cells are similar to those of extant Chinese species of Torreya . Conversely, the deep and narrow stomatal bands are most comparable to the extant North American species. Based on the rarity of the fossils within the assemblage and comparisons to the habitat preferences of extant North American Torreya , we infer that the plants likely grew on moist slopes farther away from the depositional basin. Combined with previously described conifers of this assemblage, this fossil-taxon shows that conifers were still diverse in the region during the Late Cretaceous. • Upper Cretaceous Horseshoe Canyon Formation (HCF) is highly fossiliferous. • The HCF hosts abundant silicified plant fossils within ironstone nodules. • We describe a new conifer species: Torreya albertensis (Taxaceae) from the HCF. • Torreya albertensis is a rare but distinct component of the conifer-dominated flora.